Method and apparatus for making reconstituted tobacco



Sept. 16,1969 M s. BLOCK ETAL 3,467,109

METHOD AND APPARATUS FOR MAKING RECONSTITUTED TOBACCO Filed June 12. 1967 2 Sheets-Sheet l H2O PLUS SLIVER ADDITIVES STEMS HAMMERJ MILL U.-.

SUPPLY LIQUID RETURN RECYCLE EXCESS LAYER RETURN HOLDING RELIEF TANK 3/ VALVE -24 L RECIRCULATING PUMP M 3'0 AIR azss 2a 27 SIZING N O G 4 'VACUUM PICKUP ROLLER WIRE 2 SUCHON oEvlcE 52 54 BOX 36 o 35 29 4 46 Q Q Q Q L ZZl sucnou BOX 2 5 0 L J l f INVEN'TURS. 0 CARRIER sucnou MEiAHB'ELDEBkSCgIbBURY a WIR ffig 37 4 E 3 l 80X 1 MELVIN FRANCIS REICH l h I W 2L SEPARATOR ATTORNEYS Sept. 16, 1969 M s, OCK ET AL 3,467,109

METHOD AND APPARATUS FOR MAKING RECONSTITUTED TOBACCO Filed June 12, 1967 2 Sheets-Sheet 2 VACUUM PICKUP DEVICE l x MATERIAL LAYER SUCTION BOX CARRIER a m UI ilk \wh I7a- I 475 A 4/ -14 3 5 W -I8 I8: l ,5 5 2d 7 '8; I501 :1 INVENTORS. vfifasififisaum a He 5m m FRANCIS RElCH EMA I Z I T] 2 their ATTORNEYS.

United States Patent 3,467,109 METHOD AND APPARATUS FOR MAKING RECONSTITUTED TOBACCO M Sabel Block, Bloomfield, N.J., Melvin D. Sidbury,

Greensboro, N.C., and Melvin F. Reich, New Allbany, Ind., assignors to P. Lorillard Company, Inc., New York, N.Y., a corporation of New Jersey' Filed June 12, 1967, Ser. No. 645,380 Int. Cl. A24b 9/00; D21h /06 U.S. Cl. 131-140 23 Claims ABSTRACT OF THE DISCLOSURE This invention relates to the manufacture of tobacco products and it relates particularly to the manufacture of sheet tobacco from tobacco waste products, such as, for example, tobacco leaf stems, slivers, leaf fragments, tobacco dust and the like.

In recent years, so -called reconstituted tobacco has been manufactured from the waste products of tobacco.

by any of a number of processes. One such process is essentially the same as that which is used in the manufacture of paper, in which the tobacco particles in the form of' slivers, stem fragments, leaf fragments and tobacco dust are beaten into or disintegrated into a pulp in' the presence of 40 to 50 parts of water to about one part by weight of the waste tobacco products. The resulting highly fluid pulp is discharged onto a papermaking Wire where a large proportion of the moisture is removed and then the resulting sheet is dried with heat to provide a self-sustaining sheet of tobacco. Because a large amount of water is necessary in the papermaking process, its removal is costly and renders this process uneconomical in current use.

Another process, while not requiring large quantities of water, is entirely dependent on binding materials to unite the finely divided tobacco particles into a sheet, since they are incapable of uniting and forming, by themselves, a continuous self-supporting sheet. For that reason, it has been necessary to admix with the fine tobacco paraticles substantial proportions of binders, for example, up to of suitable binders such as, for example, carboxymethylcellulose, vegetable gums and the like, to render the resulting sheet self-sustaining. Although considerable research for nontoxic, tasteless and odorless binders has been conducted, the known binders still impair the flavor of the tobacco when burned in a cigarette, cigar or pipe, and render it brittle and dark in color, so that only a small portion may be used in blends with the natural leaf. Furthermore, the cost of the binders in the relatively large proportion required is relatively high, so that as in the case of reconstituted tobacco made according to the papermaking process, the cost is higher than desirable for economical use of either process.

In Block et a1. U.S. Patent No. 3,141,462 for Processing Tobacco (issued July 21, 1964, to the assignee of this invention and application), an economical process is disclosed for reforming tobacco wastes into a generally useful tobacco product. The disadvantages of the prior processes are overcome and a greatly improved tobacco product more nearly approaching the natural leaf is obtained.

More particularly, in the process of that patent tobacco waste particles such as stems and slivers are broken down or separated into fibers of substantial length capable of forming a self-sustaining mat or felt, in which other tobacco fines, such as particles broken from tobacco leaves during processing, may be intermingled and wetted with a relatively small quantity of water to form a thick slurry, which, after drying, is self-sustaining even when completely devoid of binder. For example, the tobacco stem particles and tobacco slivers are mixed with water in the proportion of about one part of stem fragments and slivers to 6 to 13 parts by Weight of water and are defibered (separated into individual fibers) without breaking the fibers into short lengths, that is, without substantially reducing the lengths of the fibers. The fibers resulting from such a defibering operation may be as much as a quarter of an inch long and thus are capable of forming a matrix or felt of excellent strength and handling properties.

Other tobacco particles, such as No. 8s, i.e., tobacco leaf fragments which pass through a No. 14 screen (12 meshes per square inch), including tobacco dust and the like, can be added to the stems and slivers either before or at any time during the defibering operation, thereby to form a mixture of the long fibers and tiny particles in which the moisture content is about six to eight times by weight of that of its solid content. Such a mixture is in the form of a thick slurry which is formed into a layer of a thickness corresponding approximately to the thickness of leaf tobacco. The layer may then be subjected to a squeezing operation which, aided by suction, removes excess water and may then be dried in any suitable way, such as, for example, by means of infrared radiation, hot air or the like to produce a finished sheet which is highly flexible and has a good bulking density and handling properties so that it may be readily intermixed with cut cigarette tobacco or the like for producing cigarettes and other tobacco products.

The product resulting from the invention of the aforementioned patent has the light color characteristics of natural tobacco leaf, a good flavor when smoked since it contains no added binder, and a self-sustaining burning power, even in sheet form, It has a considerably higher sugar content than ordinary reconstituted tobacco manufactured by papermaking process and it has handling properties approaching natural leaf tobacco in cigarette-making operations where the material is subjected to cutting and processing in machinery which has the tendency to break down the tobacco shreds.

There is provided, in accordance with the present invention, an improvement in the method of the aforementioned patent which enables recycling all of the black water recovered from the slurry layer in the proc ess of forming and dying the sheet. More particularly, it has been found that substantially all of the black water withdrawn by suction boxes can be recycled back to the mixing tank, while still permitting the sheet to be readily removed from the wire after it has been dried, if the bond tending to form between the sheet and the wire, because of the stickiness of dissolved materials, notably sugars, in the sheet, is broken while thesheet is only partially dried by lifting the layer from the carrier surface and then replacing the layer on the surface for further drying. The black water withdrawn by suction from the layer is collected and recycled back to the soaking and mixing tank and combined with make-up water and tobacco stems and slivers to form the initial slurry which is then processed in accordance with the method of the aforementioned Block et a1. patent.

The slurry layer is formed on the upper surface of an endless, porous forming member, is sized and pressed by a sizing roller and water removed by drainage through the wire and by a suction box. The layer then traverses a part of the lower run of the member and is pulled off onto a second endless, porous member, which may be termed a carrier, where it is dried. After partial drying, the layer is picked up onto the lower surface of a pick-up member which is spaced a small distance above and travels parallel to and at the same speed as the carrier wire. The bond between the layer and the carrier member is thus broken, and the layer is then pulled back onto the carrier belt for final drying. Once the bond is initially broken, it does not reform, and the dried sheet can be readily removed from the carrier.

The improved method has increased the yield by about by weight, of the waste tobacco materials supplied, over the yield previously obtained and has thus reduced the unit cost of the final product. Moreover, the reuse of all black water, which contains dissolved materials contributing to the flavor, aroma and burning characteristics of the tobacco, permits those materials to be retained in the reconstituted sheet. The recycled liquid with the make-up water added contains a stable concentration of those materials, and the reconstituted sheet thus has a chemical composition more closely approaching that of natural strip tobacco. The improved method has enabled an increase in the concentration of various substances affecting the aroma and taste of the tobacco, approaching 100%, without affecting the ability of removing the sheet from the carrier wire in a self-sustaining, continuous form. As a further advantage of the improved method, there is virtually no waste liquid to be disposed of, an advantage of considerable significance where stream and lake pollution is a problem and waste must be treated.

Still another modification of the method involves the defibering of the tobacco stems and slivers. In the method as disclosed in the Block et al. patent, a special ultrasonic homogenizer was preferred to attain defibering without also reducing fiber length. It has now been found that a special form of disc refiner can be used. Efforts to use conventional refiner techniques have provided less fruitful.

In accordance with the invention, the blend of stems and slivers with fines and No. 8s, recycled llquid and makeup water is subjected to abrading action between a pair of discs, one of which is rotating or both of which are rotating in opposite directions. The disc surfaces are formed to define, in all radial planes through the refiner axis, tortuous paths so that the blend is retarded in its outward fiow and retention time is substantially increased over what it would be in conventional refiners. A form for the faces of the mated discs found to provide excellent results is one defining sine curves in all radial-axial planes.

For a better understanding of the present invention, reference may be made to the following description 'of an exemplary embodiment, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic flow sheet illustrating a typical method embodying the present invention;

FIG. 2 is a schematic view showing details of part of the carrier wire on which the layer is dried; and

FIG. 3 is a se'mischematic view in cross-section of a refiner for defibering the stems and slivers,

Referring now to FIGURE 1 of the drawing, tobacco stem and fragments thereof which may range' in length up to several inches are fed into a hammer mill 10 where they are broken into relatively shorter lengths, e.g., about one-eighth to one-half inch, but not ground to powder. The shorter stem particles, together with tobacco slivers, are transferred to a soaking and mixing tank 11 where liquid recycled back from the sheet-forming stage (to be described below) and make-up water are added in the proportion by weight of about 6 to 13 parts to one part of slivers and stems. Flavoring materials also may be added at this point if desired. The mixture is allowed to stand in tank 11 for a sufiicient time e.g., about one hour or longer to impregnate the stem particles and slivers with water. Thereafter, the soaked materials are discharged into a supply tank 12 which serves to feed them to a disc refiner or other defibering device 13, sometimes referred to hereinafter as homogenizer, which separates the fibers making up the stems and slivers without breaking them up into materially shorter lengths. Tobacco fines and No. 8s may be added and mixed with the stems and pieces in the supply tank 12 in an amount such that the mixture in the tank 12 contains about 6 to 8 parts liquid and one part of tobacco solids. As will be described below, the

stems and slivers are defibered by a multiplicity of passes through homogenizers by either recycling through one unit or passing through a series of units. The fines and No. 8s may be added to the soaked materials before the first or any intermediate passes.

It has been found that a special form of disc refiner provides good defibering of the stems and slivers without substantially reducing the fiber lengths, whereas conventional refiners have not given even satisfactory results. Referring to FIG. 3, the refiner 13a includes a housing 14 having an internal closed chamber which accommodates a non-rotatable, stationary back plate 15a and a nonrotatable, longitudinally slidable front plate 15b. A rotatable and longitudinally slidable center plate is keyed on a shaft 16. The faces of the center plate 15c are spaced from the faces of the end plates 15a and 15b so as to define two radially disposed passages 17a and 17b extending circumferentially around the refiner. The spacing between the plates can be varied from, for example, approximately V in. down to zero, by moving the slidable front plate 15b toward or away from the center plate, the center plate automatically centering itself between the end plates.

The mixture of tobacco stems and slivers and water is fed under pressure to the center of the refiner through an inlet passage 15d and is forced out through the passage 17a and 17b between the front and back plates 15a and 15b and the center plate 15c and is discharged through the discharge passage 15s. A series of openings 15 enable the mixture to flow from the passage 15d to the passage 17b. The surfaces of the several plates are formed to provide a tortuous shape in radial-axial planes of the passages. In the particular form shown in FIG. 3, the shape is a sine wave, and it has been found to be important for the faces of the plates to be accurately mated. In operation, the tortuous form of the radial passages impedes the flow of stems and slivers through them. To further assist in defibering the stems and slivers, the faces of the plates have relatively deep radially extending grooves 18, say in. deep. As the stems and pieces pass outwardly through the passages 17a and 17b, they are subjected to the abrading action between the relatively rotating discs and are defibered into individual fibers. The fibers, however, remain substantially unreduced in length and thus form, in the finished product, a strong durable mat. The fiber slurry is then conducted outfrom the center of the refiner housing through a conduit 19 for further processing.

By repeatedly recirculating the suspension through pump 20, the homogenizer 13 by means of a bypass line 20 connected to the conduit 19, and the supply tank 12 or by forcing it through a plurality of similar homogenib ers connected in series, a semifiuid aqueous suspension or slurry of tobacco fibers and fines is produced. This slurry is delivered to a holding tank 24 and at this stage of the operation is ready to be formed in a sheet.

As mentioned above, the moisture content of the slurry is about 6 to 8 parts liquid and one part of tobacco solids.

Due to the thick semifiuid condition of the suspension, it is preferably formed into a sheet by pumping it with a suitable high pressure pump 25 or one or more booster pumps 26 to one or more spray nozzles 27 which discharge the material downwardly through a tower 28 onto an endless moving wire 29 similar to a papermaking wire, thereby forming a thin layer L of wet tobacco particles on the wire 29. As illustrated in FIGURE 1, a recirculation line 30 having a relief valve 31 may be provided to return excess slurry from the pump 25 to the holding tank 24. A collecting pan 32 is provided below the wire 29 to catch overspray from the nozzle 27 and material initially draining from the layer L. The material collected in the pan 32 is pumped through a conduit 33 by a pump 34 back into the holding tank 24.

The upper surface of the layer L, due to the spray deposit of the tobacco fibers and particles, is somewhat rough. In order to improve its surface texture, the layer on the wire is passed below a smooth surfaced sizing roll 35 which reduces the thickness of the layer L and smooths its upper surface and helps to fill in any voids that may have occurred. Inasmuch as the moist tobacco tends to cling to the surface of the roll 35 a suction box 36 operated by a vacuum pump 37 is positioned below the wire 29 to draw the tobacco away from the roll 35 and thus prevent tobacco sticking to it. The suction box 36 also removes black water from the layer L, and this is recycled by a pump 80 through a return line 38 back to the soaking and mixing tank where it is combined with makeup water and any flavorants or other additives, if any, to form a slurry with the stems and slivers, as described above. A separator 39 in the return line 38 removes water and tobacco solids dissolved in water from the layer L; these solids can be extracted from time to time and used in the process.

The layer L is carried around to the lower run of the wire 29 and is drawn off the surface of the wire 29 onto a carrier wire 40 by a suction box 41. The suction box 41 removes further black water from the layer, and this is recycled through the return line 38 to the mixing tank.

As deposited on the wire 29, some of the fibers in the layer L protrude into the wire and form a mechanical attachment to it which would impede the removal of the sheet if the sheet were to be dried on the wire 29. The transfer of the layer, while moist, is readily accomplished and thus eliminates the problem of fiber strike-through.

The layer is carried on the carrier wire 40 through a first stage dryer 42 and emerges from it with a moisture content of about 60%. At this point, it has a consistency at which it can be lifted from the wire to break the bond tending to form between it and the wire because of the stickiness of the layer. In particular, a pickup device 44 in the form of an endless wire 46 travelling at the same speed and in the same direction as the carrier wire 40 is positioned slightly above the upper surface of the layer L. A suction box 48 creates a differential pressure across the layer effective to lift it from the surface of the wire 40 and onto the lower run of the pick-up wire 46. The layer, by reason of its consistency, sticks to the underside of the pickup wire and after travelling a short distance, is pulled back down onto the carrier wire 40 by a suction box 50. The black water removed from the layer by the suction boxes 48 and 50 is recycled through the line 38 back to the mixing tank 11. The layer is then dried in driers 52 and 54 to the desired extent and may be removed from the carrier wire 40 at the end of the run along its upper surface.

The driers 42, 52 and 54 may be of the type equipped with infrared heaters (not shown), or may be of the type in which air is circulated. The moisture content of the tobacco layer L at the end of the final drier 54 can be from about to 25%, or any content at which the layer or sheet L is self-sustaining and can be removed as a continuous sheet from the surface of the wire.

In a typical example of the process, moistened tobacco stems and slivers are mixed with and soaked in about 12 parts by weight of water for each part of. stems and slivers. The solid tobacco particles are allowed to-soak for about 30 minutes to one hour, although the soaking time can be more than one hour, and then are delivered to the supply tank 12. Fines and No. 8's are mixed in and the water-tobacco suspension is discharged into the homogenizer 13 and is recirculated therethrough about 10 to 12 times until the stems and slivers aredefibered and separated into the component fibers. The tobacco fragments supplied to the system, in a typical operation, consist of by weight about 60% stems and slivers, 20% factory by-products (tobacco fines) and 20% leaf fra ments (No. 8s) by weight, and by combining the materials in those proportions, the proportion of the solids to water in the suspension in the supply tank is about one part of solids to 8 parts of water by weight. The then homogenized and defibered aqueous suspension or slurry of tobacco solids is discharged into the holding tank 24 for supply by the pumps 25 and 26 to the spray nozzle or nozzles 27. The material discharged through the spray nozzles 27 is an aqueous suspension having the ratio of solids to "water indicated above.

The movement of the wires is so related to the temperature in the driers that the dried sheet L taken from the wire has at least 10% moisture.

The dried tobacco sheet L is light tan in color and has suflicient strength that it can be removed readily from the wire 40 and can even be folded and creased sharply due to the presence of the matrix of interlaced fibers. The lifting of the layer from the wire 40 after partial drying by the lifting system 44 is effective to disrupt any bond between the wire and the layer, so that the sheet can be removed without harming it. Little tendency for a bond to reform after having been broken has been observed.

The process and the equipment for practicing it are susceptible to considerable modification. Thus, for example, additives such as flavors, humectants, wetting agents, and the like may be introduced into the soaking tank 11 with the water supplied thereto. Some types of high frequency (supersonic) homogenizers rather than the refiner described above, may be used to disintegrate the stems and slivers into the component fibers. Moreover, instead of recirculating the suspensions of stems, slivers, fines and No. 8s through the homogenizer 13, they may be forced successively through a series of homogenizers to obtain continuous production of the slurry.

While only one spray nozzle 27 is illustrated, it will be understood that a plurality of spray nozzles may be provided in the spray column 28 when a sheet of substantial width is to be produced.

Inasmuch as tobacco dust is finely divided, it need not be added to the suspension in the mixing tank 24 but may be handled separately. Thus, the mixture of stem and sliver fibers and finely divided tobacco by-products can be sprayed on a drying surface and the tobacco dust may be then sprayed or sifted onto the wet layer prior to drying so that the fines will adhere to the layer. Likewise, the stems, the tobacco by-products and fines may be homogenized separately and the slurry of stems may be sprayed first to form a felt or mat onto which the finely divided by-products and the tobacco dust are sprayed.

While binders are not required for the production of a self-sustaining tobacco sheet, a very-small proportion of binder may be added if the sheet is to be subjected to extremely severe processing or'handling. Thus, sufficient binding agents such as an alginate can be added to the material in any of the soaking or mixing tanks as may be desired. Also, as indicated above, humectants and flavoring materials can be added in the usual ratio and they may be of any of the usual types.

Due to the low moisture content of the material undergoing treatment, drying of the sheet is greatly simplified and waste or loss of water in the process is very substantially reduced as compared with prior processes. The less 7 severe drying conditions and the lower content or complete absence of binders provides a tobacco sheet of a light brown or tan color similar to high quality cigarette tobacco which can be shredded and mixed in high proportion with other cigarette tobacco without altering the filling and burning properties, flavor or general handling characteristics of the tobacco. The recycling and use of black water removed by the Several suction boxes result in an improved product by limiting the loss of suspended and dissolved solids which contribute to the flavor and aroma of the product. Moreover, waste disposal is no longer a problem. The unit cost is also reduced, inasmuch as efficiency is increased to the point where only about 8% of the tobacco material is removed. The 8% loss arises from dissolved solids evolved as vapors during drying, loss of ragged edges at the sides of the sheet, and other minor effects, and steps can be taken to further improve efficiency.

From the foregoing description of the process and the specific example thereof, it will be understood that the process is susceptible to considerable modification.

We claim:

1. In a method of producing tobacco sheets from tobacco fragments including stem material and fines which includes the steps of separating the fibers of fiber bundles of the tobacco stem material by disintegrating the pieces of tobacco stem material while suspended in a liquid without substantially reducing the length of the fibers to form a thick semifluid mixture thereof, forming a layer of the fibers and fines, and drying the layer on a carrier surface to form a self-sustaining sheet in which the fibers are interlaced to impart strength to the sheet, the improvement comprising the steps of lifting the layer from the carrier surface while it is only partially dried to break any bond between it and the surface, replacing the layer on the surface for further drying, collecting substantially all of the liquid drawn from the sheet, and recycling such collected liquid back through the process.

2. A method according to claim 1 wherein the sheet is lifted by creating a differential pressure between the surfaces.

3. A method according to claim 1 further comprising the step of conveying the layer a predetermined distance parallel to and at the same speed as the moving carrier member while it is lifted.

4. A method according to claim 1 wherein the pieces of tobacco are disintegrated by conducting them along a tortuous path defined between relatively moving surfaces and abrading them between the surfaces as they traverse the tortuous path.

5. A method according to claim 4 wherein the path is shaped generally as a sine wave.

6. A method according to claim 4 wherein the abrading action is transverse to the tortuous path.

. 7. A method according to claim 4 wherein the relative movement between the surfaces is rotational and the path along which the tobacco pieces are conducted is defined by a space between the surfaces disposed perpendicular to and surrounding the axis of rotation, the pieces being supplied at the interior of the passage and being conducted radially outwardly in all directions through the passage.

8. In a method of producing tobacco sheets from tobacco fragments including stem material and tobacco fines which includes the steps of separating the fibers of fiber bundles of the tobacco stem material by disintegrating the pieces of tobacco stem material while suspended in a liquid without substantially reducing the length of the fibers to form a thick semifiuid mixture thereof, forming a layer of the fibers and fines on top of a porous moving forming surface, subjecting the layer to pressure and suction to compress and partially dry the layer by vacuum drawing liquid from it, and transferring the layer from the forming surface to a porous moving carrier surface, the improvement comprising the steps of partially drying the layer on the carrier surface, creating a differential pressure between the surfaces of the sheet effective to lift it from the carrier surface onto a porous moving pick-up surface to break the bond between the layer and the carrier member, conveying the sheet on the pickup surface a predetermined distance in the direction and at the speed of the carrier surface, creating a differential pressure between the surfaces of the sheet effective to replace the sheet on the carrier surface, conveying the sheet on the carrier surface for further drying and removal from the carrier surface, collecting substantially all of the liquid drawn from the layer, and recycling the collected liquid back through the process by adding it to the incoming waste tobacco stems and slivers before they are defibered.

9. A method according to claim 8 wherein the pieces of tobacco stem material are disintegrated by conducting them along tortuous radial paths emanating in all directions from a central axis and defined by the surfaces of closely .adjustably spaced relatively rotating numbers, and abrading the pieces between the surfaces as they traverse the paths.

10. A method according to claim 9 wherein the paths are shaped generally as sine wave curves.

11. Apparatus for producing tobacco sheets from tobacco fragments including stem material and fines comprising means for separating the fibers of fiber bundles of the tobacco stem material by disintegrating the pieces to tobacco stem material While suspended in a liquid without substantially reducing the length of the fibers to form a thick semifiuid mixture thereof, means for forming a layer of fibers and fines, and means for drying the layer on a carrier surface toform a self-sustaining tobacco sheet in which the fibers are interlaced to impart strength to the sheet, means for lifting the layer from the carrier surface while it is only partially dried to break any bond between it and the surface, means for replacing the layer on the surface for further drying, means for collecting substantially all of the liquid drawn from the sheet, and means for recycling such collected liquid back through the process.

12. Apparatus according to claim 11 wherein the means for lifting the layer from the carrier surface and for replacing the layer on the surface includes means for creating a differential pressure between the surfaces of the layer.

13. Apparatus according to claim 11 wherein the means for disintegrating the pieces of tobacco includes means defining a chamber, a pair of spaced-apart plates in the chamber defining a tortuous path, one of the plates being movable relative to the other to abrade the tobacco pieces between the surfaces as they traverse the tortuous path, and means for delivering the tobacco pieces suspended in a liquid and forcing them through the tortuous path.

14. Apparatus according to claim 11 wherein the means for disintegrating the tobacco pieces includes a housing defining a cylindrical chamber, a back plate in the chamber, a front plate in the chamber, a rotating center plate in the chamber disposed between and spaced closely to the front and back plates, the respective opposed faces of the plates being formed to define first and second tortuous paths of substantially uniform width extending radially in all directions across the faces of the plates, means for delivering the tobacco pieces to the radially inward part of said first and second paths, and means for withdrawing the fibers from the outer parts of the first and second paths.

15. Apparatus according to claim 14 wherein one of said front and back plates is mounted for adjustable sliding movement toward and away from the other plates.

16. Apparatus according to claim 14 wherein the respective opposed faces of the plates define sine-wave lines in all radial-axial planes.

17. Apparatus according to claim 14 wherein the respective opposed faces of the plates are formed with radial grooves.

18. Apparatus for separating at least partially the fibers of fiber bundles of tobacco stem material by disintegrating pieces of tobacco stem material while suspended in a liquid without substantially reducing the length of the fibers to form a fixed semifluid mixture thereto comprising means defining a chamber, a pair of spaced-apart plates in the chamber defining a tortuous path, at least one of the plates moving relative to the other to abrade the tobacco pieces between the faces of the plates as they traverse the tortuous path, and means for delivering the tobacco pieces suspended in a liquid and forcing them through the tortuous path.

19. Apparatus according to claim 18 wherein the chamber is generally cylindrical and one of the plates is rotatable relative to the other and defines with the other plate a tortuous path of generally sine-wave shape in all radialaxial planes and of substantially uniform width.

20. Apparatus according to claim 18 wherein chamber is cylindrical and there are in the chamber a nonrotating back plate and a nonrotating front plate and a rotating center plate disposed between and spaced closely to the front and back plate, the respective opposed faces of the plates being formed to define first and second tortuous paths of substantially uniform width extending radially in all directions across the faces of the plates.

21. Apparatus according to claim 20 wherein one of the nonrotating plates is mounted for adjustable sliding movement toward and away from the other plates.

22. Apparatus according to claim 20 wherein the respective opposed faces of the plates define sine-wave lines in all radial, axial planes.

23. Apparatus according to claim 20' wherein the respective opposed faces of the plates are formed with radial grooves.

References Cited UNITED STATES PATENTS MELVIN D. REIN, Primary Examiner US. Cl. X.R. 162-207, 36 l $3? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3 ,467 ,l09 September 16 1969 Patent No. Dated InventQr(s) M. S. BlOCk et al.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 55, "paraticles" should be particles Column 3, line 70, "stem" should be stems Column 8, line 30, (Claim 11) "to" should be 'UI LHKLD S EALED FEB 1 7 1970 7 mm m Fletcher, 11-. wmm: 1:. am. an. Attestin Offi Oomissioner of Patents 

